Rotational and vibrational relaxation of He2 a 3? + u
- 1 January 1970
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Transactions of the Faraday Society
- Vol. 66, 2921-2935
- https://doi.org/10.1039/tf9706602921
Abstract
The formation of He2a3Σ+ u, during and following an intense microwave-pulse discharge, was investigated by kinetic absorption spectroscopy. At 77 K, He2a3Σ+ u(v= 0) in high K states was formed both during and at the termination of the pulse. He2a3Σ+ u(v= 0 and l), in a Boltzmann distribution, appeared only at the pulse termination. The overall decay of He2a3Σ+ u was second order. An abnormally slow rate of rotational relaxation of He2a3Σ+ u(v= 0) was observed, corresponding to ∼106 gas kinetic collisions at 77 K. This was attributed to a dominance of the inter-molecular repulsion by the almost spherical 2s orbital of He2a3Σ+ u. Rotational relaxation of 3He 4He a3Σ+ was faster by about 10 fold. The vibrational relaxation rate of He2a3Σ+ u(v= 1) was also abnormally slow, indicating a “soft” intermolecular repulsion.Keywords
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